1. Field of the Invention
The present invention relates to a stereoscopic image display device, and more particularly to a stereoscopic image display device for displaying a plurality of images having a parallax therebetween to allow stereoscopic viewing of the images. The invention also relates to a stereoscopic imaging device for capturing images from multiple viewpoints. The invention also relates to a stereoscopic effect control method and a stereoscopic image display method.
2. Description of the Related Art
Techniques to display an image to allow stereoscopic viewing of the image using a plurality of images having a parallax therebetween (a multi-viewpoint image) are known. The multi-viewpoint image includes images captured from two or more viewpoints, typically, a right-eye image and a left-eye image. The multi-viewpoint image can be obtained by capturing the same subject from different positions. The images included in the multi-viewpoint image are combined to generate a stereoscopic image. The stereoscopic display of the stereoscopic image is achieved by using a parallax between the images.
Several specific systems for achieving the stereoscopic display are known. For example, parallel viewing is known as a system that allows stereoscopic display viewed with naked eyes. In parallel viewing, stereoscopic display is achieved by arranging the plurality of images side by side. Further, as systems for achieving the stereoscopic viewing using eye glasses, an anaglyph system and a polarizing filter system are known. In the anaglyph system, a stereoscopic image is generated by combining the plurality of images by superimposing the images one on the other with changing the color of the images, such as into red and blue. In this case, the stereoscopic display of the image can be achieved by viewing the stereoscopic image through red-and-blue glasses. In the polarizing filter system, a stereoscopic image is generated by combining the plurality of images by superimposing the images with different polarization directions one on the other. In the polarizing filter system, the stereoscopic display of the image can be achieved by viewing the stereoscopic image through polarization glasses.
Besides the above-described systems, a parallax barrier system and a lenticular system are known. In these systems, a stereoscopic image is generated by cutting the plurality of images into thin vertical strips and alternately arranging the strips of the images. In the parallax barrier system and the lenticular system, the stereoscopic image is displayed on a stereoscopic display monitor, which allows the stereoscopic viewing without need of the polarization glasses, or the like. Further, a liquid crystal shutter system and a scanning backlight system are known. In the liquid crystal shutter system, the stereoscopic display is achieved by alternately displaying the right-eye image and the left-eye image on a display screen, and driving liquid crystal shutter glasses synchronously with the switching of the displayed image. In the scanning backlight system, optical elements are attached on the display surface of a liquid crystal display device, and the left and right images are alternately displayed at a high speed with different directions of light beams, thereby achieving the stereoscopic display using the afterimage effect.
In general, when a relative offset between the left-eye image and the right-eye image of a stereoscopic image is changed, the stereoscopic effect felt by the user viewing the stereoscopic image changes. That is, a three-dimensional depth of an object in the image felt by the user changes. With respect to the stereoscopic display, it is preferred that the user viewing a stereoscopically displayed image can control the stereoscopic effect. This is because that different users have different preferences about the stereoscopic effect. Some users may prefer a strong stereoscopic effect (a stereoscopic display with enhanced three-dimensional depth), while other users may prefer a moderate stereoscopic effect. Further, the stereoscopic effect felt by the user depends on the user who is viewing the stereoscopic display, and the stereoscopic effect felt by different users viewing the same stereoscopic image may not always be the same.
Japanese Unexamined Patent Publication Nos. 2004-129186 and 10(1998)-090814 (hereinafter, Patent Documents 1 and 2, respectively) disclose performing stereoscopic effect control (parallax control). A stereoscopic image data processing device disclosed in Patent Document 1 includes a three-dimensional depth control unit, which serves as a stereoscopic effect control means. The three-dimensional depth control unit receives an instruction to control the parallax of a stereoscopic image that is stereoscopically displayed. The user operates a three-dimensional depth control bar while viewing a preview display to control the parallax so that a preferred stereoscopic effect is provided. The stereoscopic image data processing device combines the left-eye image and the right-eye image according to a parallax control value determined by the user, and converts the combined image into a stereoscopically displayable format and outputs the converted image. A stereoscopic camera disclosed in Patent Document 2 includes a display means that can perform stereoscopic display. With the technique disclosed in Patent Document 2, such a display means is used to always display a stereoscopic image during a photographing operation, thereby allowing control of the stereoscopic effect of the image during the photographing operation.
Japanese Unexamined Patent Publication No. 2004-180069 (hereinafter, Patent Document 3) discloses a stereoscopic image display device which sets an offset (parallax) between displayed images. The image signal thereof includes a right-eye image and a left-eye image, and suitable size information. The suitable size information is information about a screen size that is suitable for displaying a stereoscopic image. The stereoscopic image display device sets an offset between the right-eye image and the left-eye image based on the suitable size information included in the image signal and information (screen size information) about a display area of a display unit that displays the image. Patent Document 3 teaches that this allows providing a stereoscopic image with an optimal stereoscopic level (depth level) that is controlled depending on the screen size of the display unit. Further, Patent Document 3 teaches that the left-eye image and the right-eye image are displayed with being offset from each other according to a stereoscopic level instructed by the viewer, and the viewer can control the parallax so that an optimal stereoscopic effect is provided.
In the techniques disclosed in Patent Documents 1 and 2, the right-eye image and the left-eye image are combined after the parallax is controlled, and the combined image is converted into a predetermined format before being outputted. Therefore, the techniques disclosed in Patent Documents 1 and 2 do not allow controlling the once controlled stereoscopic effect later. In contrast, with the technique disclosed in Patent Document 3, the right-eye image and the left-eye image are separately delivered. Therefore, with the technique disclosed in Patent Document 3, the stereoscopic effect can arbitrarily be controlled based on the image signal. However, Patent Document 3 does not mention storing the controlled stereoscopic effect. Therefore, with the technique disclosed in Patent Document 3, even when a preferred stereoscopic effect is achieved through the control, it is necessary to control the stereoscopic effect again when the image is viewed later.
Although this is not a known technique, Japanese Patent Application No. 2009-084719 proposes a method for recording a parallax control value associated with an image. Use of this technique allows arbitrarily controlling the stereoscopic effect and using the controlled stereoscopic effect to view the controlled image later. Using the technique disclosed in Japanese Patent Application No. 2009-084719, the stereoscopic effect of an image captured with an imaging device is controlled during the photographing operation, for example, and the control value resulting from the stereoscopic effect control is associated with the captured image and recorded, so that the stereoscopic effect controlled during the photographing operation can be used later to display the image on a display device.
Now, a case where the stereoscopic effect control of a certain image is performed more than once using a plurality of devices with the technique disclosed in Japanese Patent Application No. 2009-084719, and two or more control values are recorded for the same image is discussed. The display monitors of the devices used to control the stereoscopic effect may have different sizes. For example, in a case where the stereoscopic effect control of the image is performed using three devices and three stereoscopic effect control values are recorded, the three stereoscopic effect control values may have been controlled by the user viewing display monitors having three different monitor sizes.
In a case where the image is displayed on a monitor having the same size as the size of a monitor used to control the stereoscopic effect, the user can view the image displayed with a preferred stereoscopic effect which has been set when the stereoscopic effect is controlled. However, in a case where the image is displayed on a monitor having a size different from the size of a monitor used to control the stereoscopic effect, the user views the image with a different stereoscopic effect from one achieved when the stereoscopic effect is controlled. This is because that, even when the stereoscopic image is generated according to the same stereoscopic effect control value, the stereoscopic effect felt by the user viewing the image varies depending on the size of the display monitor.
The difference of the monitor size is not considered in Japanese Patent Application No. 2009-084719. For example, if three stereoscopic effect control values, which have been controlled with three monitor sizes, are associated with an image and recorded, the stereoscopic effect control values are associated with the image and recorded without being particularly distinguished. That is, each stereoscopic effect control value is recorded in a recording medium in a state where the size of the monitor used to set each stereoscopic effect control value is unclear. Therefore, even when a stereoscopic effect control value that has been controlled with the same monitor size as the size of the display monitor used to display the image is associated with the image and recorded, the stereoscopic effect control value cannot be read out and set for displaying the image.